Wave guide direction changer



July 10, 1956 J. F. ZALESKI 2,754,483

WAVE GUIDE DIRECTION CHANGER Filed Dec. 29, 1951 IN V EN TOR. JOHN/72965544 By W) 7/% United States Patent C) WAVE GUIDE DIRECTION CHANGER John F. Zaleski, Valhalla, N. Y., assignor to General Precision Laboratory Incorporated, a corporation of New York Application December 29, 1951, Serial No. 264,093

11 Claims. (Cl. 333-98) This invention pertains to wave guide direction changers and more particularly to compact devices for changing the direction of wave guide microwave transmission and at the same time changing the direction of polarization of the microwave energy.

When microwave equipment employs hollow guides for interconnection of its components the guides must bviously be shaped and formed not only in straight runs but also in other forms. In general these forms consist of E-plane bends, H-plane bends and twists. All of these forms take considerable space since, in order to keep loss to reasonable amounts, a 90 twist or bend should be made in a length of not less than twice one wavelength in the guide (2k This requirement is, however, in violent conflict with the requirement for extreme compactness that often exists in the design of microwave equipment.

When an axial direction change of 90 is required in combination with a 90 twist or rotation of the plane of polarization a tandem combination of two of these forms is required. For example, a particular situation may call for an E-plane bend follower by a 90 twist of the guide around its own axis. There is no theoretical reason why the twist and turn cannot be combined in a single length of guide but this is never done because of the difficulty of fabrication.

This invention in one form employs a right angle turn in hollow rectangular guide combined with a 90 rotation of the guide around its longitudinal axis, so that a 90 direction change combined with a 90 twist or rotation of polarization are effected in the smallest possible space. Special and exceedingly simple means are employed within the component which virtually eliminate reflections and which at the same time provide relatively broadband operation. These means can also be employed in other constructions which are similar in requiring excitation from a wave guide in a direction perpendicular to the broad faces of the guide.

This invention can also be employed with round guide operated in the TE1,1 mode in the right-angled transition from round to rectangular guide.

The principal object of this invention then is to provide a compact wave guide component for changing the direction of microwave propagation and at the same time changing the plane of polarization.

More specifically the object of this inventionis to provide a compact right-angled wave guide component that rotates the plane of polarization by 90.

Another object of this invention is to provide a rectangular guide sharp right-angled bend that also rotates the plane of polarization of transmitted microwave energy by 90.

Another object is 'to provide an arrangement whereby two rectangular guides may be joined at a right angle and with their longitudinal median planes also'at a right angle, transmission therethrough being highly eflicient and relatively broadband. i i

"ice

Another object is to provide an arrangement whereby two round guides may be joined at a right angle for transmission in the TE1,1 mode with phase rotation.

Still another object is to provide an efiicient side outlet transition from round to rectangular guide.

A further understanding of this invention may be secured from the detailed description and associated drawings in which:

Fig. 1 depicts two rectangular wave guides joined at a right angle with the direction of polarization of microwave energy therein twisted Fig. 2 is a cross-sectional view taken on the lines 2-2 of Fig. 1.

Fig. 3 illustrates a device producing a reverse twist in energy polarization.

Fig. 4 illustrates the application of the invention to a window in a guide.

Fig. 5 illustrates the application of the invention to a radiating slot.

Fig. 6 depicts application of the invention to a round guide and a rectangular guide joined at a right angle.

Referring now to Fig. 1, a hollow rectangular guide 11 is joined at right angles to a second hollow rectangular guide 12 so that the plane through the longitudinal median lines of the broad sides of wave guide 11 is at right angles to the similar plane of wave guide 12. This configuration is thus equivalent to a combined 90 bend and 90 twist joined in tandem. One end of the guide 11 is terminated in a conductive plate 13, the distance D from the inner surface of the plate 13 to the longitudinal axis of the guide 12 being made equal to one-quarter wavelength in guide although it can also be made any odd integral multiple of this distance. A straight conductive rod or post 14 is inserted through the guide walls at the center of the junction line 16 between the two guides and in the plane of the median lines of the broad sides of guide 12. The post 14 is secured to the guide structure in such a manner as to be at a 45-degree angle as respects the broad side 17 of the guide 11. The rod is therefore also at an angle of 45 with the broad side 18 of the guide 12, and is made of such length as to end approximately at the intersection of the axes of the two guides. For example, in one instance using 0.9 inch by 0.4 inch guide excited at 8800 mcps, the length of the rod inside the guide was .248 inch.

A wedge-shaped fillet 19 is added for strength at the point where the rod 14 is secured in the walls of the guides. The free end of the rod preferably has somewhat rounded edges to reduce corona. The construction is shown more clearly in the cross-section of Fig. 2, the rod 14 being at an angle of 45 with the longitudinal axis 21 of the guide 12.

The diameter of the rod is inch, although it can have any lesser diameter consistent with stiifness or can be slightly larger. However, its diameter is preferably not greater than inch in wave guide of the 0.9 x 0.4" size, with a proportionate maximum in wave guides of other sizes. That portion of the rod 14 extendingoutside of the inner surface of the walls of the guide constitutes merely a mechanical support and has no electrical function. w

In operation, let it be supposed that microwave energy of any frequency suitable for use with rectangular guide of the size employed is applied to the open end 22 of the guide 11 by any means, such as by connecting the end 22 by means of a conventional flange joint to the output of a microwave generator. The microwave energy afi'ects the rod 14 as if it were an antenna projecting into the guide perpendicular to a broad side of the guide, because the direction of protrusion of the rod has an orthogonal component perpendicular to the guide side 17. Currents 3 therefore are induced in the rod 14. These currents produce a field about the rod and the electric part of this field has an orthogonal component perpendicular to the broad side 13 of the guide 12. The field can therefore be propagated in the guide 12. This action is aided by the action of the end plate 13 which places a standing wave voltage maximum point at the rod 14. The resulting action by which the rod 14 causes microwave energy propagation in guide 12 is so efficient that there is substantially no more loss in the device than in an equivalent length of straight guide. For example, in one instance the voltage standing wave ratio over a 2 4% frequency band as measured at input was less than 1.05, indicating a power loss at any frequency within this band of not more than 0.0006 watt per applied watt.

The length of the guide arm 11 may be made as small as the width W (Fig. 1) of the guide 12 plus the amount by which the end 13 of the guide 11 projects beyond the guide 12 when it does project at all. The length of the guide arm 12 need be only as much as required for mechanicial reasons in assembly with associated equipment. Therefore the total length in 0.9 x 0.4" guide need be only slightly greater than one inch, and this component can thus be made much more compact than an equivalent twist and a turn connected in tandem having a minimum length of eight inches.

The phase of the output microwave power depends upon the side of the guide structure into which the rod is inserted. For example, if in Fig. 2 the phase of the microwave power emitted from the arm 12 has a certain angle relative to the phase of the energy applied to the arm 11 at its end 22, Fig. 1, then in Fig. 3, in which the rod is inserted in the opposite side of a similar guide structure, the phase of the output will have an angle displaced l80 from that of the output of Fig. 2.

The microwave guide construction of the invention can be used reversibly. If microwave energy be applied to the open end 23 of the arm 12, Fig. 1, the energy will be transmitted to the open end 22v of the arm 11 just as effectively as if transmitted in the opposite direction.

If in the 90 angle component described in connection with Fig. l a window be placed across the guide 12 at its junction with the guide 11, the microwave energy will be changed in direction and in polarization as before described. However, since in general windows are reactive to a degree and in sense depending on size and shape, conventional matching means may be added to avoid reflections caused by the window. Such a window is depicted in Fig. 4 at 24, with a second or matching window at 25 in the guide 12 parallel to window 24 at a distance A of approximately one-half wavelength in guide from it.

The window 24 of Fig. 4 may be formed as a longitudinal slot in the center of the guide 11, dispensing with the arm 12, resulting in the construction of Fig. 5. A pin 27 is inserted through the broad side 28 of the arm 11 at a 45 angle in a transverse plane through the center of the slot 26, the distance D from the plane of the pin 27 to an end plate 29 being made approximately In the absence of the pin 27, such a slot at the center line of the broad face 23 of a guide propagating energy in the dominant mode does not radiate to external space When energy is applied to the open input end 22 of the guide 11. However, addition of thepin 27 at an angle of approximately 45 causes the guide to be coupled to the slot, which then radiates part or all of the energy applied to the guide. In this case the degree of coupling to the slot can be conveniently controlled by adjustment of the length of the pin 27 thatprotrudes intothe guide or adjustment of theangleofinsertiou Qf .th e p ir 1,

the angle of 45 being optimum for broad-baud coupling.

One application of this embodiment is in the design of an antenna array having a series of longitudinal slots in at least one of the broad faces. If all slots are at the median line and each is provided with a 45 rod as described, all will radiate, the radiation of each depending on the energy applied and the degree of coupling to the guide as controlled by the length of the coupling rod.

The polarity of excitation depends in such cases on which side of the slot the rod is on. Such a slot can also be coupled and made to radiate by displacing it from the median line, the polarity of radiation depending on the direction of displacement. Various combinations of displacement coupling and of rod coupling can therefore be made for special purposes.

An E-plane longitudinal slot in round guide can be made to radiate by the application of a coupling rod analogous to the manner described in connection with rectangular guide. A slot array also can be constructed with radiation of each slot controlled by the length of coupling rod.

A useful application of this invention is in the design of a side arm transition between round guide and rectangular guide. Such a transition is depicted in Fig. 6, in which a round guide 31 is joined to a rectangular guide 32 positioned to serve as a shunt arm. The end 33 of the round guide 31 is closed with a conductive plate at about one-quarter-wave distance from the axis of guide 32. When the input end 34 of round guide 31 is energized in the TE1,1 mode with polarization in the plane of the rectangular guide axis, no energy is transferred to the rectangular guide 32 in the absence of a coupling rod. However, when a coupling rod 36 is inserted radially h through the wall of guide 31 in the transverse plane that includes the axis of guide 32 andis at 45 to that axis, substantially all input energy is coupled to the rectangular guide 32, where the energy is available at the output end 37. This device is also reversible, the guide end 37 then serving as input and the end 34 as output.

What is claimed is:

1. A microwave direction changer comprising, a first rectangular wave guide section, a conductive plate terminating one end thereof, a second rectangular wave guide section joined to said first wave guide section at right angles thereto, an aperture in the wall of said first wave guide section at the junction of said second wave guide section providing communication between the interior spaces thereof, said second wave guide section having its longer transverse dimension parallel with the longitudinal dimension of said first wave guide section, said first rectangular wave guide section having its lesser cross-sectional dimension parallel with the longitudinal dimension of said second wave guide section said first and second wave guide sections being adapted for excitation by microwave energy in the TEi,o mode, an elongated conductive member conductively connected to and projecting interiorly of said first wave guide section from a junction edge of said first and second wave guide sections, said member having its longitudinal axis lying in a plane comprehending the longitudinal axis of said second wave guide section and extending transversely of said first wave guide section and said member being at an angle of 45 degrees as respects the longitudinal axis of said second wave guide member.

2. A microwave direction changer comprising, a first rectangular wave guide section, a conductive plate terminating one end thereof, a second rectangular wave guide section joined to said first wave guide'section at right angles thereto, an aperture in the wall of said first wave guide section at the junction of said second wave guide section providing communication between the interior spaces thereof, said second waveguide section having its longqlj transverse. dimension. parallelwith the longitudinal dimension of said first wave guide section said rst and second wave guide sections being adapted for excitation by microwave energy in the TE1,0 mode, an elongated conductive member conductively connected to and projecting interiorly of said first wave guide section from a junction edge of said first and second wave guide sections, said member having its longitudinal axis lying in a plane comprehending the longitudinal axis of said second wave guide section and extending transversely of said first wave guide section, said member extending at an angle of 45 degrees as respects the longitudinal axis of said second wave guide section and being positioned a distance of an odd multiple of quarter wavelengths in the guide from said conductive plate.

3. A microwave direction changer in accordance with claim 2 in which said elongated conductive member has a length such that the end thereof lies substantially at the intersection of the longitudinal axes of said first and second wave guide sections.

4. A microwave direction changer comprising, a round wave guide section, a conductive plate terminating one end thereof, a rectangular wave guide section extending at right angles to said round wave guide section with its longer transverse dimension parallel to the axis of said round wave guide section, an elongated conductive member having its longitudinal axis lying in a plane comprehending the longitudinal axis of said rectangular wave guide section and extending transversely to said round wave guide section, said member being conductively connected to and projecting interiorly of said round wave guide section at an angle of 45 degrees as respects the longitudinal axis of said rectangular wave guide section, said conductive plate being positioned an odd multiple of quarter wavelengths in the wave guide from said conductive member.

5. A microwave guide direction changer comprising, a first hollow wave guide section, a second hollow rectangular wave guide section joined to said first wave guide section at right angles thereto with its longer transverse dimension parallel with the longitudinal dimension of said first wave guide section, a generally rectangular aperture in the wall of said first wave guide section at the junction of said wave guide sections providing communication between the field spaces thereof, an elongated conductive member conductively fastened to the wall of said first wave guide section adjacent said junction and projecting into the interior of said first wave guide section at an acute angle to the longitudinal axis of said second wave guide section, said conductive member having its longitudinal axis lying in a plane which comprehends the longitudinal axis of said second wave guide section and is normal to the longitudinal axis of said first wave guide section.

6. A microwave guide direction changer in accordance with claim 5 in which said first hollow wave guide is circular in cross section.

7. A microwave guide direction changer in accordance with claim 5 in which said first hollow wave guide is rectangular in cross section.

8. A microwave guide direction changer in accordance with claim 5 in which said conductive member is a conductive rod.

9. A microwave guide direction changer comprising, a first rectangular hollow wave guide section, a second rectangular hollow wave guide section having an end thereof joined to a broad side wall of said first wave guide section and extending normal thereto with its longer transverse dimension extending along the length of said first wave guide section, a rectangular aperture in the broad wall of said first wave guide section at the junction of said wave guide sections, said aperture having its longer dimension extending in a direction parallel to the longer transverse dimension of said second wave guide section and providing communication between the field spaces of said first and second wave guide sections, an elongated conductive member conductively secured to the wall of said first wave guide section and projecting into the interior thereof at said junction at an acute angle as respects the axis of said second wave guide section, said conductive member having its longitudinal axis lying in a plane which comprehends the longitudinal axis of said second wave guide section and is normal to the longitudinal axis of said first wave guide section.

10. A microwave guide direction changer in accordance with claim 9 in which said acute angle is substantially 45.

11. A microwave direction changer comprising, a first rectangular waveguide section, a second rectangular waveguide section joined to a broad side of said first waveguide section at right angles thereto with its longer transverse dimension extending along the length of said first waveguide section, a rectangular aperture in the broad side of said first waveguide section at the junction of said Waveguide sections providing communication between the field spaces thereof, a conductive member conductively connected to and extending into the interior of said first waveguide section at said junction extending at an acute angle as respects the longitudinal axis of said second waveguide section and centered on a plane normal to the longitudinal axis of said first waveguide section and parallel to the longitudinal axis of said second waveguide section.

References Cited in the file of this patent UNITED STATES PATENTS 2,458,579 Feldman Jan. 11, 1949 2,606,248 Dicke Aug. 5, 1952 2,632,808 Lawson Mar. 24, 1953 2,668,191 Cohn Feb. 2, 1954 2,713,151 Farr July 12, 1955 OTHER REFERENCES Ragan: Microwave Transmission Circuits, vol. 9, Radiation Laboratory Series, pp. 675-76 relied on. 

